CVE-2017-18083 in Confluence Server
Summary
by MITRE
The editinword resource in Atlassian Confluence Server before version 6.4.0 allows remote attackers to inject arbitrary HTML or JavaScript via a cross site scripting (XSS) vulnerability through the contents of an uploaded file.
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Analysis
by VulDB Data Team • 01/01/2020
The vulnerability identified as CVE-2017-18083 represents a critical cross site scripting flaw within Atlassian Confluence Server's editinword resource functionality. This vulnerability affects versions prior to 6.4.0 and enables remote attackers to execute malicious code through crafted file uploads that contain HTML or JavaScript payloads. The flaw exists in the processing of uploaded files within the Confluence Server environment, specifically within the editinword component that handles document editing operations. The vulnerability stems from insufficient input validation and output encoding mechanisms that fail to properly sanitize user-supplied content before rendering it within the web interface.
The technical implementation of this XSS vulnerability occurs when Confluence Server processes files uploaded through the editinword resource without adequate sanitization of content. Attackers can exploit this by uploading malicious files containing script tags or other HTML elements that get executed in the context of other users' browsers when they view the uploaded content. This type of vulnerability falls under CWE-79 which defines Cross-Site Scripting as a weakness where untrusted data is sent to a user agent without proper validation or encoding, allowing malicious scripts to be executed in the victim's browser. The attack vector leverages the web application's failure to properly escape or filter user-controllable input that gets rendered back to users, creating an environment where persistent or reflected XSS attacks can occur.
The operational impact of this vulnerability extends beyond simple script execution as it can enable attackers to perform a wide range of malicious activities within the Confluence environment. An attacker could potentially steal session cookies, redirect users to malicious sites, modify content displayed to other users, or even escalate privileges within the Confluence application. The vulnerability is particularly dangerous in enterprise environments where Confluence servers often contain sensitive business information and where users may have elevated permissions. The attack can be executed remotely without requiring authentication, making it a significant threat to organizations that have not patched their Confluence installations. According to ATT&CK framework, this vulnerability maps to T1059.007 for Scripting and T1566 for Phishing, as attackers can use the XSS to deliver malicious payloads and gain unauthorized access to user sessions.
Organizations should prioritize immediate patching of Confluence Server installations to version 6.4.0 or later to remediate this vulnerability. The patch addresses the root cause by implementing proper input validation and output encoding mechanisms that prevent malicious content from being executed. Additional mitigations include implementing web application firewalls to detect and block suspicious file upload patterns, restricting file upload capabilities where possible, and enforcing strict content security policies. Security teams should also monitor for any signs of exploitation attempts and conduct regular vulnerability assessments to identify similar issues in other applications. The vulnerability serves as a reminder of the importance of proper input validation and output encoding in web applications, particularly those handling user-generated content, and demonstrates how seemingly minor implementation flaws can lead to significant security breaches in enterprise collaboration platforms.